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I have a wall switch that currently controls a wall outlet. I don't have or want a light plugged into that outlet. I'm comfortable reconfiguring the circuit so that the outlet is powered directly and the switch is out of the picture -- both ends of the switch go to the outlet gang box so it's easy to bypass. However, what I'd really like is for the switch to toggle a computer-controlled light on a different circuit. I just need the switch to send a signal when pressed.

I'm looking at a switch like an Inovelli Red with a "Smart Bulb Mode" which doesn't disconnect the load but just sends a signal to an automation hub. Sounds like what I want. Unfortunately, this house does not have a dedicated neutral wire in the switch box.

What I'm thinking of doing is using the two wires (+ground) that run between the outlet and the switch to wire the smart switch with live and neutral as if it were another outlet, and not connect anything to the switch's load terminals. The switch's own circuitry would always be powered, so I could have it send a signal like I want, and I wouldn't care what it did with its load because there'd be no circuit to close.

Does that make sense / is it safe?

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3 Answers 3

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That is possible. under specific circumstances.

Currently you have a switch loop between the outlet and the switch. These are usually done with a marked white and a black in the US.

If that is the case then you can remove the mark on the white and use it as a neutral. You will need to move the marked white to the neutral at the other end of the switch loop (aka the outlet being controlled).

If however they used black and red you cannot use either as a neutral.

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  • If there is a red and black, there should also be a white neutral.
    – crip659
    Aug 24, 2023 at 11:54
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    @crip659 not always, if it's individual wires in conduit then the electrician might have pulled a black and red without neutral. Aug 24, 2023 at 12:13
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    But if it's conduit, a neutral can always be added.
    – Ecnerwal
    Aug 24, 2023 at 13:01
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    the colors of wires depend on the country...
    – JB.
    Aug 25, 2023 at 12:36
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First, the building codes require you have physical switches in most rooms that allow a person to be able to turn on a light. Code is not particular about the underlying mechanism. It does not apply to every light in the room, as long as one switch operates a light you're fine.

Your plan is to re-task the switch loop to be always-hot and neutral, to power a smart-switch "remote". It then uses radio or power line coded signaling to actually control the light. That is perfectly acceptable, as long as it provides the above function. An example of smart switches which do this is Insteon.

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Yes, you can do that. Thanks to LEDs. Why? Because older motion sensors, timers, etc. (the predecessors, in a sense, of the modern smart switch) would often leak current through the switched hot in order to power themselves. That does not work well with LEDs (results in faint glow, blinking, premature failure of the lights, etc.). As a result, most new smart switches are designed to get power some other way. That can include:

  • Ground - But only if UL or ETL agrees. While it is likely that any "needs neutral" smart switch would function if connected to ground instead of neutral, that is not safe or code compliant. However, there are some switches which legitimately power themselves through hot + ground.
  • Battery - That actually works well for some types of switches, particularly well-designed wireless remotes. (Not WiFi - that draws too much power for the battery to last a long time.)
  • Neutral - This is the best way to do it, because you have no limitations on the amount of current (except the total circuit capacity, of course).

As you seem to have described, you can basically repurpose the white wire to be neutral. How exactly to do that will depend on the existing wiring, but generally it requires some rearranging of things either at a light fixture junction box or at a receptacle box.

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  • Missing reference for: particularly well-designed wireless remotes. (Not WiFi - that draws too much power for the battery to last a long time.)
    – Traveler
    Aug 24, 2023 at 18:36
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    @Ruskes Which part do you take issue with? 802.11's fundamental unsuitability for low power applications is well known, and there's plenty of Zigbee switches which last for a decade on a button cell.
    – Sneftel
    Aug 24, 2023 at 19:14
  • I'd disagree there. Modern hardware saves power well, and I'm at about 6 or so months on the 2 wifi wireless remotes with a pair of AAAs so far. Aug 25, 2023 at 7:51

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